The invention which is the subject of the application is an electrosurgical tool of a type which can be used to perform electrosurgical functions such as incisions and/or coagulation of body tissue and/or fluids and can be used in conjunction with electrical generating and control apparatus to provide an advantageous function such as cutting and/or coagulating operation to be performed.
Electrosurgery is generally defined as the use of radio frequency (RF) current to cut tissue and control bleeding and the process has been employed in open operative procedures for many years and it has become the most widely used cutting and coagulation technique for minimally invasive surgery.
In conventional electrosurgical cutting apparatus, and in particular cutting tools, it is known to utilise a cutting tool having an active or supply electrode and a second, or return, electrode. In one arrangement the return electrode is provided in the form of a plate upon which the patient on whom the surgery is being performed lies. This can be dangerous to the patient and can, upon malfunction, cause burns.
Though versatile, cost effective, and popular, electrosurgery techniques can compromise patient safety under certain circumstances. The surgeon may directly burn non-targeted internal organs or tissue upon unintended contact of the tip of the tool through imprecise mechanical operation of a laparoscopic instrument. In addition stray electrical currents emanating from the tool can inadvertently burn non-targeted tissues beyond the surgeon""s limited field of vision and such stray energy burns can occur regardless of the surgeon""s skill and judgement. Stray electrical currents may be released either through direct coupling or if the electrical insulation that coats the active electrode fails due to degradation or damage. Another electrical phenomenon known as capacitive coupling can instantaneously transfer significant amounts of stray electrical current to non-targeted tissue, causing injuries which are located outside the restricted keyhole view of the laparoscope, and thus may go undetected by the surgeon. The symptoms of injury can be delayed in onset for several days, thereby obscuring the underlying cause. The complications resulting from internal electrosurgical burn injuries compounded by delay in diagnosis and treatment can have a profound medical and economic impact on patients. Electrosurgical burns can also result from the phenomenon of capacitive coupling, which occurs when electrical current is induced from the active electrode to nearby conductive material, despite intact insulation. During electrosurgery, the charge on the active electrode switches from highly positive to highly negative at a very high frequency. The rapidly varying electrical field around the active electrode is only partially impeded by electrical insulation and creates stray electrical currents by alternately attracting and repelling ions in surrounding body tissue. Currents transferred in this way in nearby tissue can cause irreversible damage. The movement of electrically charged ions in capacitively coupled tissue can cause currents that can heat tissue sufficiently to produce a burn. Thus it is clear that the combination of the design of the conventional instruments, the limited field of vision during laparoscopy, and the nature of the electrosurgical environment, can cause even the most skilled surgeon to inadvertently burn a patient.
One commonly used type of electrosurgery is known as Monopolar electrosurgery, and a diagram illustrating this is included as Prior Art Diagram 1, which has traditionally been used primarily as a method of hemostasis during surgery. The technique gets its name from the single electrode used to delivery electrical energy from the current generator to the patient. A concentrated electrical current is delivered from the tip of the electrode to targeted tissues, causing a controlled burn that stops bleeding. With this technique, the electricity then disperses and flows through the patient, to be returned to the electrosurgical unit (ESU) via a large return electrode pad or plate attached to the patient""s skin at a remote location. By varying the voltage, current, or waveform of the electrical energy delivered by the electrode, surgeons can cut tissue cleanly (a xe2x80x9cpure cutxe2x80x9d), coagulate tissue to stop bleeding, or produce a xe2x80x9cblended cutxe2x80x9d that combines these two functions. Finally, a dispersed coagulation mode known as fulguration allows coagulation of diffuse bleeding, which may be desirable when operating on highly vascular tissues. This range of surgical modes, in addition to superior efficacy for coagulation, makes Monopolar electrosurgery the dominant and most advantageous minimally invasive surgery technique.
An alternative form of electrosurgery is bipolar electrosurgery, and a diagram of the same is included as prior art diagram 2, in which there is provided a tool on which both the active and return electrodes are mounted, delivering energy to tissues between the two electrodes upon contact with the tissue by the two electrodes so that the electrosurgical function takes place between the two electrodes and which causes the frequent blockage between the two electrodes due to cut body tissue and other material and therefore means that there is frequent inability to perform the electrosurgical function as both electrodes are required to actually perform the function. Unlike Monopolar electrosurgery, bipolar electrosurgery is not an effective method for making a xe2x80x9cpure cut.xe2x80x9d Furthermore, the bipolar technique cannot be used to stop bleeding over a large area. In order to achieve hemostasis in bipolar surgery, it is necessary to grasp tissue between both the active and return electrodes.
The aim of the present invention is to provide an improved electrosurgical tool which can be used for electrosurgical work with the electrodes mounted within the tool in a manner which allows improved operation and control of the same. It is also particularly sought that the tool can be operated with a control means which analyses and reacts to impedance characteristics of the tissue during operation of the apparatus and controls the power supply to the tool in response to analysis and interpretation of the same.
In a first aspect of the invention there is provided an electrosurgical tool, said tool comprising a housing in which is provided electrical connections to a power supply, and the tool includes a supply or active electrode, and a return electrode, and a working end for performing an electrosurgical function, and wherein the working end is formed by the end of the active electrode and return electrode and the active electrode performs the electrosurgical function.
In one embodiment the active electrode in use is in contact with the body tissue of a patient and there is a gap between the end of the return electrode of the tool and the body tissue. Typically the working end of the active electrode protrudes beyond the working end of the return electrode. In one preferred embodiment the supply or active electrode is mounted in the tool so that the end of this electrode protrudes beyond the end of the housing.
Typically in whichever embodiment of the tool, in the supply of power to the tool from the generator to which it is connected there is a change in phase between the active and return electrodes in use of the electrosurgical tool.
In a further embodiment, the ends of both the active and return electrodes contact the body tissue and in this embodiment the return electrode is positioned on the body tissue prior to the active electrode so as to minimise risk of burn to the patient.
Typically, the active electrode is mounted within and substantially surrounded by the return electrode which in one preferred arrangement is formed in a substantially annular form with the active electrode mounted to pass through the centre of the same. In one arrangement the return electrode comprises a series of components in one example, four electrode components, each provided to lie within 90 degree sectors of the annular arrangement. Typically the ends of the components of the return electrode are angled and/or curved to control the directivity of the RF field generated at the working end of the tool.
Typically the return electrode components are arranged in pairs of phased positive and negative arrangements. In one embodiment two of the four components are provided as phased negative components and two are phased positive components.
Typically the active electrode is spaced from contact with the return electrode arrangement. In one embodiment the spacing is maintained by insulating material which can be of any material which can withstand the voltage being applied along the electrodes. In one embodiment the material used is a ceramics material.
It is envisaged that the electrodes are mountable in a body which is formed of an insulating material, in one embodiment by moulding, and which body is provided with means to allow the same to be electrically connected to the electrodes. It is envisaged that the electrodes can be manufactured of any suitable material, one being high grade stainless steel. Typically the housing of the tool is releasably attached with the body thereby allowing the housing to be connected to a body of the required length for the surgical work to be performed and so the housing may be connected to a number of different tool bodies. The housing is typically formed from tubing such as stainless steel tubing and this surrounds the insulating material and the electrodes.
The housing or body can also, in one embodiment, be provided with engagement and electrical contact means into which the return and/or active electrode can be inserted. The housing is also provided with electrical contact and mechanical engagement means which allow the housing to be connected mechanically and electrically to the tool body.
In one embodiment the active electrode is provided with a surgical formation at the working end which, when the electrode is in position, protrudes from the tool and is formed to allow a specific electrosurgical function to be performed. Typically a range of electrodes with differing surgical formations can be provided and fitted to suit specific requirements and said surgical formation can include knife edge, point, ball or hook formations. The surgeon can therefore interchange electrodes to suit particular surgical requirements. In an alternative embodiment a common electrode can be used with engagement means to allow engagement with any of a range of surgical formations at the working end.
The tool in accordance with this invention can be used in various embodiments for use in open surgery, minimal access surgery, Neurosurgical and transluminal percutaneous treatment of vessel occlusion and speciality surgical fields
In a further aspect of the invention there is provided an electrosurgical tool, said tool comprising an active electrode and a return electrode in parallel and connected to an electric current and electric current control means and characterised in that the electrical current is split using a biphasic RF output and the split is controlled in response to the impedance measurement of the active electrode.
In one embodiment the biphasic array of the return electrode within the RF/EM field is used as the return pathway and the Radiofrequency [RF] energy is directed using impedance controlled by a biphasic RF/EM Field surrounding a central or offset active electrode.
In one embodiment the electrosurgical tool in accordance with this invention is used in conjunction with a control means in the form of an electrosurgical generator which utilises dynamic impedance feedback and adaptive algorithm techniques together with a waveguided biphasic RF/EM energy to generate a phased energy field around the active electrode of the tool. One such electrosurgical generator is described in the applicants patent EP0830095.